1. Field of the Invention
The invention relates to an underground sliding sleeve for fracturing the oil-gas well, and more particularly to a multi-level sliding sleeve of ball-throwing open type.
2. Description of the Related Art
Staged fracturing of multi-level sliding sleeve packer is the leading technique of well completion among the staged fracturing techniques of open-hole horizontal wells, which can realize the simultaneous fracturing of several segments of the horizontal well without using the bridge plug packer. Well completion of ball-throwing sliding sleeve is a kind of completion method which can be realized through mechanical and hydraulic operations. The method enables the sliding sleeve and the expansible packer to divide the horizontal segment into several independent systems according to the geological requirements. During construction, balls will be thrown in order, and pressure is built to open the sliding sleeve, thereby connecting to the segment where the sliding sleeve is, packing the fractured segments and realizing staged fracturing.
Conventionally, the sliding sleeve is opened by the thrust force of balls. Then the balls are blocked by the ball socket, and cannot move to the next sliding sleeve with the matching size. In consequence, in the current staged fracturing techniques using multi-level sliding sleeve packer, one ball-throwing can only open the one ball-throwing sliding sleeve corresponding thereto; in the meanwhile, as limited by the ball differential, the construction tube mechanism can only carry a limited number of sliding sleeves, thereby failing to provide enough production fairways in the horizontal well with a long horizontal segment.